This invention is directed to the field of limited slip differentials of the type for connecting a vehicle""s driving shaft to a pair of driven shafts, more particularly to a modified clutch pack mechanism located outside the differential case in a housing extension.
The present invention relates to an improved limited slip differential, of the type used in automotive applications, offering greater torque than achievable with conventional limited slip differentials. Limited slip differentials, as known in the art, are necessary for good traction. For example, when an automobile goes around a corner, the outer driving wheel must be turned at a greater speed than the inner one. This is achieved through the differential. It lies midway between the two driving wheels, linked to each wheel by a half-shaft turned through a bevel gear. The half-shafts have sun gears connected by free-wheeling planet pinions. When traveling straight, the planet pinions do not spin and drive both half-shafts at the same speed. As the automobile corners, the planet pinions do spin, driving the sun gear and half-shafts at different speeds.
Such differential systems have been improved over the years. Of particular concern to automotive engineers is the problem of traction, such as when one driving wheel encounters ice, mud, or snow, and the like. In straight, dry driving conditions, the differential supplies equal torque to each half-shaft. However, when adverse driving conditions are encountered, such as operating on a slippery surface, prior art differentials, supplying equal torque to the driving wheels resulted in reduced traction even when only one driving wheel was exposed to the slippery road surface. This dangerous condition resulted in the development of differential systems that introduced a torque to the system.
The prior art contains a number of references directed to improvements to limited slip differential systems, especially as to safety performance in the operation of vehicles so equipped with the systems. A first type of limited slip differentials to which improvements have been proposed are those which include a pair of aligned driven shafts, having side gears splined thereto, where rotation of a drive shaft is transmitted through a differential case and spider gears to the respective side gears. Further, each driven shaft includes a clutch pack, with interleaved clutch plates, where the plates are alternately splined to the case and the side gears. In operation, rotation is transmitted from the case through the clutch plates to the side gear to increase the torque of the driven shaft of the wheel having the greater traction and thereby rotate the wheel having the greater traction.
A second type of limited slip differentials are those which incorporate a single multi-plate clutch assembly that is operably connected to the pair of driven shafts. The clutch assembly is actuated in response to the magnitude of speed differentiation between the pair of driven shafts.
a.) One type of differential assembly employs a hydraulically-operable locking differential having a friction-pack arrangement for locking an output shaft and associated side gear with the differential housing. In the invention use is made of a piston-cylinder motor the axis of which is colinear with the output shaft. The advantage, therefore, is that the locking operation may be effected while the drive and output shafts are rotating without stopping the vehicle.
b.) another assembly relates to a vehicle friction material condition measurement system that includes a sensor which responds to both changes in working length and temperature. The sensor is embedded in a friction lining to provide a signal indicative of both wear and temperature to an electronic control unit which interprets long term averaged change in the sensor resistance. Such resistance may be measured when the vehicle is stationary as lining wear and short term changes in sensor resistance are representative of lining temperature.
c.) a third assembly is directed to an automotive differential gear arrangement with a driven rotatable differential housing wheel driving opposed bevel gears within the housing, differential bevel gears in driving engagement with the opposed bevel gears, and a clutch between the housing and one of the shafts of the opposed bevel gears for partially or completely blocking the differential gear arrangement. The clutch is a cone clutch disposed between the bearings supporting the housing, with a frictional surface mean diameter that is larger than the internal diameter of the housing, and is provided with a spring for constant biased engagement. Also, wedging means are provided to increase the clutch frictional engagement upon relative rotation between clutch surfaces.
d.) a fourth assembly teaches a limited slip differential mechanism which is engageable or disengageable at the option of the vehicle operator. The mechanism operates through a friction disk clutch arrangement, which controls the relative rotative speeds of the vehicle wheels and related axle shafts, while permitting a release of the friction disk clutch arrangement and relative rotation of the vehicle wheels, and related axle shafts upon predetermined road conditions and vehicle operation.
While the foregoing prior art disclose the use of a limited slip clutch pack located outside the main cavity of the differential case, they fail to disclose
The manner by which the present invention is capable of achieving the greater torque, and hence improved safety, will become apparent from the following specification, particularly when read in conjunction with the accompanying drawings.
This invention relates to a limited slip differential assembly for the operative rotation of a pair of aligned driven wheel axles of a vehicle, where the assembly provides greater torque capability to the vehicle by the ability to use larger than conventional sized clutch plate sets. The assembly comprises a case supporting at least one pinion gear and side gears driven to rotate about an axis by the at least one pinion, where each side gear drives a respective axle. The modified assembly includes a case containing at least one pinion gear and side gears, a planetary gear set, and means for driving a pair of driven wheels. Further, the housing includes an extension surrounding one of the driven wheels, where the driven wheel mounts a large diameter clutch pack set consisting of alternating metal plates, such as made of steel, and friction discs within the housing extensions. The assembly further includes a gear set between the case and the clutch pack set, where the gear set comprises an outer ring gear, an inner ring gear, and plural planetary gears therebetween in rotative relationship with the outer and inner ring gears. Further, the clutch pack set is sandwiched between a pair of spring biased pressure pads, which are mounted within a rotating plate, where the metal plates of the clutch pack are secured for rotative movement by the rotating plate.
The present invention is directed to a limited slip differential assembly that offers greater torque capability through the use of larger than conventional clutch plates. A pair of planetary gears disposed between a side gear and a rotatable collar, which in turn is disposed about an inner extension of the differential case with the clutch plates splined thereto. By this unique arrangement, the clutch plates are located outside of the differential case and results in a limited slip differential capable of receiving clutch plates of a much larger diameter than with conventional limited slip differentials, to thereby allow for greater torque.